This application claims the priority of Korean Patent Application No. 2003-4107 filed on Jan. 21, 2003 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.
1. Field of the Invention
The present invention relates to a data storage device such as a hard disk drive, and more particularly, to an actuator latch apparatus for a data storage device which can prevent an actuator from being rotated by an external impact by locking the actuator at a predetermined position when the rotation of a disk is stopped.
2. Description of the Related Art
A hard disk drive (HDD) which is one of data storage devices for a computer reproduces data from a disk or records data on the disk by using a read/write head. In the hard disk drive, the head is moved to a desired position by the actuator in a state of being raised from a recording surface of the rotating disk to a predetermined height, thus performing its functions.
When the hard disk drive is not operated, that is, the rotation of the disk is stopped, to prevent the head from colliding against the recording surface of the disk, the head is parked at a position out of the recording surface of the disk. The head parking system can be classified into a CSS (contact start stop) system and a ramp loading system. The CSS system is to form a landing zone at an inner circumferential side of the disk, where data is not recorded, and park the head so as to contact the landing zone. According to the ramp loading system, a ramp is installed at an outer side of the disk and the head is parked on the ramp.
However, in a state in which the head is parked in the landing zone of a disk or on the ramp, when an external impact or vibration is applied to the disk drive, the actuator is arbitrarily rotated so as to escape from the landing zone or ramp and move toward the recording surface of the disk. In this case, the head contacts the recording surface of the disk so that the head and/or the recording surface of the disk may be damaged. Thus, when the rotation of the disk is stopped and the head is parked in the landing zone or on the ramp, the actuator needs to be locked at a predetermined position not to be rotated arbitrarily. For this purpose, a variety of actuator latch apparatuses are provided.
In the CSS system, a magnet latch apparatus is typically used. The magnet latch apparatus locks an actuator at a desired position, that is, at a parking position, using a magnetic force of a permanent magnet. In the magnet latch apparatus, a strong magnetic force is required to obtain a stronger latch force in order to stably lock the actuator. However, to operate the disk drive, the head needs to be moved toward the recording surface of the disk. For this purpose, the locking state of the actuator must be removed. Here, since torque applied to the actuator increases as the latch force increases, as soon as the locking state is removed, the actuator rotates excessively by inertia and vibrates severely. To prevent the excessive rotation, a braking force needs to be applied to the rotating actuator at the same time when the locking state of the actuator is removed. Such accurate control of the actuator is very difficult. Thus, there is a limit to the latch force in the conventional magnet latch apparatus and accordingly it is difficult to appropriately to react to a strong external impact.
To solve the above problems, a dual latch apparatus using an inertial latch and a magnet latch has been suggested, an example of which is shown in FIG. 1. A dual latch apparatus shown in FIG. 1 is applied to a hard disk drive having a head parking system in a CSS system and is disclosed in U.S. Pat. No. 6,400,533.
Referring to FIG. 1, a disk drive 10 has a disk 12, or a plurality of disks, installed at a spindle motor 14. An actuator 18 moves a read/write head 16 to a desired position on the disk 12 and is rotatably installed on a base plate 20. A landing zone 28 where the head 16 is parked and no data is recorded is provided in an inner circumferential side of the disk 12. A data zone 30 where data is recorded is provided outside the landing zone 28. As shown in the drawing, a magnet latch apparatus 44 and an inertial latch apparatus 60 to lock the actuator 18 when the head 16 is parked in the landing zone 28 are provided in the disk drive.
The magnet latch apparatus 44 to react to a relatively weak impact or vibration includes a magnet 40 and a metal stopper 42. The inertial latch apparatus 60 to react to a relatively strong impact includes a first latch member 62 installed on a base plate 20 capable of pivoting and a second latch member 64 provided at an end portion of an actuator arm 24. When a strong rotational shock is applied to the disk drive 10, the first latch member 62 pivots by inertia to interfere with the second latch member 64 so that the actuator 18 is prevented from being rotated arbitrarily,
However, it is difficult to apply the conventional inertial latch apparatus 60 having the above structure to a compact mobile disk drive due to its large size occupying a large space. Also, since the inertial latch apparatus 60 can react to a relatively strong rotational impact only, to react to a relatively weak impact and vibration, the magnet latch apparatus 44 is additionally needed. Thus, the entire structure of the disk drive 10 is complicated and the cost for assembly and the time therefor increase.
In the meantime, U.S. Pat. No. 6,163,440 discloses an inertial latch apparatus adopted to a ramp loading type disk drive. Since the inertial latch apparatus is made up of numerous parts such as an inertial lever and a latch lever, the structure thereof is complex and a large space is required. Also, since the inertial latch apparatus can react to a relatively strong rotational impact as described above, a magnet latch apparatus is needed as an additional latch apparatus to react to a relatively weak impact and vibration.
FIG. 2 illustrates an active latch apparatus using an electromagnet disclosed in U.S. Pat. No. 5,812,345.
Referring to FIG. 2, a disk drive 70 includes an actuator 72 installed in a housing 78. The actuator 72 moves a read/write head to a predetermined position of a disk. A coil 76 of a voice motor (not shown) is installed at one end portion of the actuator 72. An active latch apparatus 80 has a latch arm 82 installed at a frame 90. The latch arm 82 is installed capable of pivoting around a pivot pin 94 in a direction perpendicular to a direction in which the actuator 72 rotates. A permanent magnet 92 is installed at one end portion of the latch arm 82 and a latch member 88 is provided at the other end portion thereof. The active latch apparatus 80 has an electromagnet 96 which is separated a predetermined distance from the permanent magnet 92.
When the actuator 72 is parked in the landing zone of a disk, the latch arm 82 pivots in a predetermined direction by a magnetic force of the permanent magnet 92. Accordingly, the latch member 88 of the latch arm 82 is hooked by a latch tab 84 provided at one end portion of the actuator 72 so that the actuator 72 is locked not to be arbitrarily rotated. When an electric power is applied to the electromagnet 96, the latch arm 82 rotates in the opposite direction so that the actuator 72 is unlocked and can rotate.
However, the active latch apparatus 80 having the above conventional structure needs the permanent magnet 92 and the electromagnet 96 to operate the latch arm 82. Accordingly, an additional electric power and on/off control thereof for the operation of the electromagnet 96 are required. Furthermore, since the active latch apparatus 80 has a complex structure and occupies a large space due to its large size, it is difficult to apply the active latch apparatus 80 to a compact mobile disk drive.